20 Why the World Trade Center Towers Collapsed

Question 1

Unprotected steel warps, sags, bends, and collapses when heated to normal fire temps of about _________.

Answer 1

1,100 to 1,200 degrees F

Question 2

John T. O’Hagan in his book High-Rise Fire and Life Safety in 1976 listed the following problems of spray on fire protection of steel:

Answer 2

1. Failure to prepare the steel for spray on coating adhesion
2. Poor or uneven application
3. Variation of spray-on material during manufacture makes it ineffective
4. Lack of thoroughness in covering the stell during application
5. Failure to replace spray on material dislodged by other tradespeople
6. The spray on fire retardant must adhere to the steel

Question 3

What is a phase III elevator?

Answer 3

An elevator that is enclosed by walls that protect it from toxic fumes, smoke, fire, and water.

Question 4

What is the weak link in today’s high-rise buildings?

Answer 4

Floor construction